Florida Highlands Freshwater Marsh

This system represents non-tidal marsh vegetation in the peninsula of Florida and in the Tallahassee area. These highland marshes occupy different types of depressions such as former lake basins, shallow peat-filled valleys, and zones around existing natural lakes. The marshes and the basins they occur within are unstable over time due to subsurface subsidence and drainage pattern changes. In some examples, surface waterflow is generally lacking due to the presence of limestone near the surface, but water levels have fluctuated greatly over time. Soils range from mucky surfaces to sandy loams or sands, but slowly permeable subsoils contribute to the presence of standing water for much of the year. The vegetation mosaic includes a range of mostly herbaceous plant communities that may be referred to as marshes, meadows, and prairies, collectively comprising a relatively diverse number of associations. Permanent water bodies support a range of submerged and floating aquatic species. Areas with approximately a meter of standing water tend to support dense stands of emergent herbaceous perennials, often in monospecific stands; species include Typha latifolia, Pontederia cordata, Nelumbo lutea, and others. Where there is less water (usually present only during wet season), more graminoid vegetation is present, with species such as Panicum hemitomon, Leersia hexandra, and others. With historic water level fluctuations, the vegetation mosaic has also changed, sometimes quite rapidly.

A relatively diverse assemblage of vegetation is present, ranging from open water communities to emergent and graminoid marshes, and scattered shrublands. Placing all component associations is difficult due to a number of factors; the current list (12-02) is incomplete. In the absence of fire, portions of stands will become dominated by Salix caroliniana. If fire continues to be absent, these areas may succeed to Acer rubrum until a replacement fire or mechanical activity restores the marsh.

The concentric zones or bands of vegetation are related to length of the hydroperiod and depth of flooding. The outer, or driest, zone is often occupied by sparse herbaceous vegetation consisting of Aristida palustris, Rhynchospora microcarpa, Rhynchospora cephalantha, Rhynchospora tracyi, Rhynchospora filifolia, etc., Xyris elliottii, the subshrub Hypericum myrtifolium, and patches of Amphicarpum muehlenbergianum or Spartina bakeri. This sparse zone may be followed downslope by a sparse to dense zone of Hypericum fasciculatum, Stillingia aquatica, and scattered herbs, such as Xyris fimbriata, Eriocaulon compressum, Eriocaulon decangulare, Rhynchospora inundata, and Eleocharis baldwinii. The innermost, deepest zone is occupied by Panicum hemitomon, Pontederia cordata, Sagittaria lancifolia, or Cladium mariscus ssp. jamaicense (= Cladium jamaicense). Floating-leaved plants, such as Nymphaea odorata, may be found in open water portions of the marsh. Depending on depth and configuration, depression marshes can have varying combinations of these zones and species within each zone.

These highland marshes occupy different types of depressions such as former lake basins, shallow peat-filled valleys, and zones around existing natural lakes (Kushlan 1990). The marshes and the basins they occur within are unstable over time due to subsurface subsidence and drainage pattern changes. Soils range from mucky surfaces to sandy loams or sands, but slowly permeable subsoils contribute to the presence of standing water for much of the year.

In some examples, surface waterflow is generally lacking due to the presence of limestone near the surface, but water levels have fluctuated greatly over time (Patton and Judd 1986). In the absence of fire, portions of stands will become dominated by Salix caroliniana. If fire continues to be absent, these areas may succeed to Acer rubrum until a replacement fire or mechanical activity restores the marsh. Paynes Prairie is a large permanently protected example of highland marsh. Water-control structures allow the manipulation of water levels in Paynes Prairie to achieve ecosystem management goals (Kushlan 1990).

Drainage is the biggest threat to highland marshes, but many have been grazed by cattle and some have been mined for peat (Kushlan 1990). Nutrient-laden runoff from adjacent developed or agricultural land is a threat to many highland marshes (Kushlan 1990). Invasive exotic plants are also a threat.

This system is found in the Florida Peninsula and in the Tallahassee Hills/Valdosta Limesink area, possibly ranging into adjacent Georgia. See map in Kushlan (1990, p. 327).